1. Technical Field of the Invention
The present invention relates to erosion control blankets and, more particularly, to a soil erosion control blanket having a synthetic, fibrous filler material which is substantially non-biodegradable. The erosion control blanket of the present invention is designed to prevent soil erosion and runoff, as well as permitting the in-growth of grasses and other vegetation, while retaining a near original state and not degrading significantly over a number of years.
2. History of the Related Art
Erosion control blankets have established commercial acceptance and use worldwide. Erosion control blankets are articles which resemble a form of fibrous matting in which two outer layers of netting or other material are commonly used to form an envelope or covering about a fibrous interior filler layer. These blankets are commonly used to reduce soil erosion and runoff from erosion-prone areas such as highway embankments or water drainage ditches.
Several different styles of erosion control blankets or mats are commonly in use today. One particular style of blanket that does not use a netting material is set forth and shown in U.S. Pat. No. 5,786,281 which is assigned to the assignee of the present invention and incorporated herein by reference. Other styles may include at least two outer netting or facing layers that are filled with a loose fibrous material. For example, one particularly effective erosion control blanket is the CURLEX or excelsior fiber blanket manufactured and sold by the American Excelsior Company of Arlington, Tex. since 1964. This blanket is fabricated in elongated rectangular mat form, from elongated, randomly intertwined wood fibers commonly referred to as excelsior. Prior art erosion control blankets and mats such as these are commonly used in conjunction with commercial or residential construction projects in an attempt to control soil loss and runoff into adjoining areas. The blankets are unrolled along the earth area to be protected against erosion, and are secured along the sides of one another and to the underlying ground area with a series of conventional ground staple members. The ground staple members may be made of steel, wood, plastic or other materials and serve to anchor the mats securely to the covered earth area. Additionally, in some applications, erosion control blankets or mats such as these may be rolled to form a sort of artificial curb or barrier at the edge of a property or construction site.
The netting and loose fiber filler construction permits blankets or mats of this kind to be fairly light in weight and also to permit the ingrowth of grasses and other vegetation into and through the blanket. The netting primarily serves to hold the loose fiber filler together while providing a large number of openings for plant ingrowth. As these blankets will frequently become a fixture in their installment site, it is often desirable to form the inner fibrous layer of the blanket of various types of biodegradable materials. By way of example, recycled paper or fiberized waste paper, wood fibers or excelsior, straw or other naturally fibrous materials such as coconut husks may be used to provide a biodegradable filler material. However, in some erosion-prone areas such as water runoff ditches and the like, it is particularly useful to have an erosion control blanket or mat with a more substantial and permanent filling which will not significantly degrade over long periods of time.
One solution to the problem referenced above is the use of polymeric or other synthetic fibers as filler materials. Some synthetic filler materials which have been suggested include polyethylene, polypropylene or nylon fibers and blends of fibers such as these with organic or biodegradable fibers such as those noted above. Several shortcomings have been noted by end users with these blankets which include synthetic fibers in that the blankets tend to become matted down or thinner over time and tend to lose their loft or three-dimensionality. As blankets become matted down, the fibers in the filler tend to become more tightly packed, and the subsequent in-growth of grasses and other vegetation becomes increasingly difficult. Prior art attempts to resolve fiber matting problems have involved the use of multiple netting layers disposed throughout the filler material and netting which is corrugated or shaped to hold a more three-dimensional structure. However, these solutions may involve significant additional material and labor costs to produce an erosion control blanket. Moreover, synthetic/organic blended fillers tend to degrade over time much like organic-only fillers, and merely do so at a slower rate. Thus, while synthetic-only fillers for erosion control blankets have been suggested, these appear to be somewhat wasteful of natural resources and still suffer from shortcomings in the areas of fiber resiliency and loft.